The speed at which you build your bus depends a lot on budget. If you can afford all new materials and appliances all at once off the bat, you can get it done pretty quick if you're working full time. Hell you can hire people to help and get it done in a few weeks if you were really set out to do it that way.
For the rest of us, taking the build slower means we can save money. We don't need to hire any help, and can source lots of the material for free or cheap second hand. I was just looking on craigslist and found a ton of usable stuff for bus conversions. Wood, appliances, pipe, etc. By going slower you will end up with a finished product you're happier with too. You can play around with different layouts, and make changes that are needed as you discover them. And you will never discover them any other way than by spending time in the bus. Your greatest ideas will come out of necessity, which won't happen until you need for something.
And as it was stated, watch a ton of videos on bus conversions and tiny homes. Read build threads here and you will learn from others mistakes before they become your own.
I guess the most important point is don't strive to be 100% done by a specific date. Let it happen organicly and be okay with living in an evolving build. This will also lighten the workload, since you will be doing little projects here and there instead of grueling days and weeks. You can really focus on the little details, which are huge in tiny spaces.
I admire your bravery though, knowing you lack the experience and skills to do something and still going for it is a noble human quality. I also find myself the most interested in things I don't understand and study and practice them (often obsessively) until I do.
http://www.skoolie.net/forums/showthread.php?t=9883 - 7.3L 4x4 Shuttle Bus Toyhauler conversion